Exit Activities and Discontinued Operations - Narrative (Details) - USD ($) $ in Millions		3 Months Ended			9 Months Ended		24 Months Ended
	Oct. 01, 2021	Dec. 31, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021
Discontinued Operations, Held-for-sale | EnerBank
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain from divestiture of business			$ (3)	$ 0	$ (8)	$ 0
Discontinued Operations, Held-for-sale | EnerBank | Subsequent Event
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from divestiture of businesses	$ 1,000
Discontinued Operations, Held-for-sale | EnerBank | Forecast | Subsequent Event
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain from divestiture of business		$ 660
Retention Benefits | D.E. Karn Generating Complex
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Expected cost			35		35		$ 35
Retention and severance costs					0	11	16
Costs incurred and capitalized					1	$ 1
Retention Benefits | D.E. Karn Generating Complex | Retention Incentive Program
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Regulatory asset			$ 5		$ 5		5
Retention Benefits | D.E. Karn Generating Complex | Property, Plant and Equipment
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Costs incurred and capitalized							$ 4